Integrated circuits are being produced in large numbers in the form of flat chips which are usually square and which have terminal areas or terminal pads located on one surface thereof, usually along the side edges of the chip. These chips are being produced in several sizes and having varying numbers of terminal areas. When a chip is packaged in a chip carrier, it is of course necessary to establish electrical connections to each of the terminal areas on the chip and to provide conductors extending from the chip to the edge of the chip carrier so that the chip can be connected to further circuitry.
In accordance with conventional packaging techniques, it is necessary to provide a lead frame for each chip size and terminal area requirement. Thus, it is necessary to provide different lead frames for each of the many sizes of chips being supplied to the industry. The requirement of a specifically tailored lead frame and chip carrier for each size of chip is obviously a burdensome inconvenience to the electronic packaging industry. Clearly, substantial economies could be achieved if a single standard lead frame and chip carrier housing could be used with chips in a range of sizes and chips having a range of numbers of terminal areas of pads thereon. The present invention is directed to the achievement of a lead frame and a chip carrier which can in fact be used in the packaging of chips of varying size and having varying numbers of terminal areas or terminal pads thereon.
A lead frame in accordance with the invention comprises a support portion located at the geometric center of the lead frame and leads which are integral with, and extend from, the support portion in all directions. The leads are of two classes, simple and composite, the simple leads comprising a single very narror strip of metal which extends from one of the edges of the central support portion. Each composite lead comprises a trunk lead and branch leads. The trunk end of each composite lead extends from one corner of the support postion of the lead frame and the branch leads extend from the side edges of the trunk lead at spaced intervals. The simple leads and the branch leads have a configuration such that their intermediate portions and outer ends form a symmetrical radiating pattern with reference to the central support portion of the lead frame.
The chip carrier housing comprises a frame-like structure which is molded into intermediate portions of all of the leads in surrounding relationship to the central support portion. The molded housing has an integral thin web which extends inwardly to the central support portion and which serves to support the leads. When an integrated circuit chip of a relatively small size and having a mimimum number of terminal pads on its surface is to be packaged in accordance with the invention, the central support portion is removed along with the web material which in supporting relationship to the central support portion, the chip is placed in the resulting opening and the simple leads only are connected to the terminal areas or pads of the chip. If a larger chip having a greater number of terminal pads is to be packaged, the inner end portions of the simple leads are removed and a portion of each trunk lead is removed. The removal of a portion of each trunk lead makes available some of the branch leads for establishing electrical connections to the chip. The larger the opening in the center of the lead frame is made, the greater the number of branch leads which become available and a range of sizes and types of integrated circuit chips can therefore be accommodated with a single lead frame and chip carrier housing.